Imagine you’re living with a small group of early humans around 100,000 years ago. Your band consists of several families, who have survived together for decades. There’s lots to eat around your camp and plenty of fresh water. Weather’s not too bad. There are a few other encampments up and down the river. They are good people to visit every once a while. You share ideas, trade resources and your young often mix.

Sounds like a pretty wonderful life, right? But something awful is about to happen. Your mate’s brother went off with several of the children to teach them how to track antelope. One of the children doesn’t return that day. The boy slipped and fell off a craggy ridge. Your mate’s brother is beside himself with grief and guilt. But it’s nothing compared to that of the child’s parents. Their pain overwhelms them. They demand answers. Why wasn’t their child watched more closely? How could this have happened?

The incident festers over the next moons. Your mate’s brother is blamed. He is constantly harassed by the family of the lost children. An open wound develops. People take sides. Your mate understands the parents’ hurt, as do you. But it’s not right to keep chiding your mate’s brother. He’s a responsible hunter. Accidents happen.

Eventually threats are made and small fights break out. Hatred and mistrust spread. Someone is hurt in a fight. Reparations are demanded and refused. Your camp has split into two. Living together has become difficult.

One evening you hear a troubling rumor. One of the men closely related to the parents of the lost child is seen preparing poisoned arrows. What could they be for? Poison isn’t good for hunting because it can taint the meat. The man is questioned and insists he means to kill a couple lynx he noticed prowling close to camp. But no one else saw the lynx. No tracks are found. Your mate doesn’t believe the man. Does he have a more sinister purpose?

Your family doesn’t feel safe anymore. It’s time to leave. You pack your things and head north. Many join you.

The scenario described above is familiar. As humans we know our emotions often lead to unfortunate consequences. We believe the story because we can see how it would happen. And yet, in the natural world outside of human communities, this kind of occurrence is non-existent. Other species simply don’t behave in this manner. Only humans can let their pain drive them apart. Or their fear, or jealousy. Or a host of other ominous feelings.

While the tragedy described above is terrible, such situations may have led to positive results in the story of the human family. The people who head north discover new lands. Homo sapiens eventually populate the entire livable world.

This is the theory presented by Dr. Penny Spikins, of the Department of Archaeology at the University of New York. She postulates it was fear of ourselves that drove people to so quickly inhabit the entire earth around 100,000 years ago. Before that time, human migrations were slow, a function of ecological change and population growth. More importantly, earlier migrations were stymied by geologic barriers like steep mountain ranges, ice fields and oceans.

Around 100,000 years ago though, humans overcame these barriers and spread in every direction. Did inter-tribal conflict drive us apart? Read more about Dr. Spikins theory and decide if it makes sense to you.